Worm Breeder's Gazette 13(4): 41 (October 1, 1994)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
|1||Biology Dept., Syracuse University, Syracuse, NY 13244|
|2||Biology Dept., John Carroll University, Cleveland, OH 44118.|
|3||Biology Dept., Syracuse University, Syracuse, NY 13244|
We have previously reported the isolation of recessive, extragenic mutations that enhance the extremely weak mutant phenotype of glp-1 ( bn18 )at 20260 to produce a severe Glp-1 phenotype (Madison, '93; Baltimore, '94). We call these enhancers ego mutations, for enhancer of glp-1 .We have subsequently characterized a set of ten mutations representing seven genes, ego( om13 ,27) IVC, ego( om14 ,23, 24) IR, ego( om18 )IC, ego( om30 )IIIRC, ego( om31 )IIIRC, ego( om33 )IRC, and ego( om40 )VC. Currently, we are attempting to isolate more alleles of some of these genes using noncomplementation screens, we are also continuing our enhancer screen. As described below, mutations in five ego loci cause a variety of germline defects in a glp-1 (+)background; they are oogenesis defective (Ooc) steriles, and some have other defects as well. In contrast, mutations in two other genes do not produce obvious mutant defects in a glp-1 (+)background. ego( om14 ,23, 24) are alleles of glp-4 ;they fail to complement glp-4 ( bn2ts )for an Ooc phenotype at 20260 and a Glp phenotype at 25260. Although they do not show the glp-4 ( bn2 )Glp phenotype, they do produce defective oocytes similar to those found by Beanan & Strome [Devt:755-766 (1992)] to be produced in glp-4 ( bn2 )hermaphrodites that have been shifted to restrictive temperature as adults. In om14 mutants, cellularization of oocytes appears to fail; DAPI staining reveals a gradual accumulation of diakinesis nuclei in the proximal gonad throughout adulthood. By ~3 days into adulthood, many of these nuclei develop what appears to be an Oar phenotype. We are now examining the glp-4 phenotype in males. om18 and om40 mutants contain several common features. The number of germ cells in both mutants at the L3 /L4molt is ~30% of the N2 number. By young adulthood, they have ~50% as many germ cells as do N2 animals. Despite their reduced germ lines, mitotic nuclei are clearly visible in the distal germ line of both mutants several days into adulthood. Spermatogenesis is delayed in both males and hermaphrodites, as well. However, in om18 mutants the spermatogenesis delay reflects a delay in onset of meiosis whereas in om40 meiosis it does not. We are examining L4 om40 animals to determine if the spermatogenesis delay reflects an abnormally long arrest in pachytene. Both mutants produce small, irregularly sized oocytes that do not become fertilized. om40 mutants have two other defects that may be related; the somatic gonad is abnormal, and the proximal germ line undergoes extensive mitotic proliferation. In both sexes, the proximal mitotic germ cells eventually go through meiosis and spermatogenesis. ego( om30 )and ego( om31 )mutant hermaphrodites have a stronger Glp phenotype than do om18 and om40 mutants; at the young adult stage they have ~30% as many germ cells as do N2 animals. Unlike om18 and om40 mutants, the defective oocytes produced by om30 and om31 mutants are often fertilized; the resulting embryos typically die in early embryogenesis. ego( om13 ,27) maps very close to two other genes of interest, lag-1 and sog-3 .Complementation tests indicate that both alleles may interact with lag-1 ( q385 ):at least some trans heterozygotes have a Glp phenotype and/or vulva defect in a glp-1 (+/-)background. At present, it is not clear whether the ego mutations are extremely weak alleles of lag- 1 or are alleles of another locus that interacts with lag-1 .In either case this result is encouraging because lag-1 is thought to function in the glp-1 / lin-12 mediated signaling pathway(s) in at least some tissues [Lambie & Kimble (1991) Devt 112:231-240]. In contrast, ego( om13 )complements sog-3 ( q294 )for suppression and enhancement of glp-1 (ts)as well as for any visible germline phenotype. We are mapping om13 more precisely and producing a closely marked stock for further phenotypic and genetic analysis. We are especially interested in repeating the lag-1 complementation test in a glp-1 (+)background. ego( om33 )interacts with both glp- 1 and glp-4 .Although om33 and glp-4 ( om14 )complement in a glp-1 (+)background, they fail to complement for enhancement of glp-1 ( bn18 )(i.e., om33 +/+ glp-4 ( om14 ); glp-1 ( bn18 )animals are Glp-1 ).We have recently isolated several more enhancers that interact with both glp-1 and glp-4 ;we are mapping these alleles and testing for interactions among them and with om33 .We are also screening directly for mutations that are allelic to om33 .